It was, as acts of desecration go, not quite in the same league as the Goths' sacking of Rome.

Yesterday, at 12.58pm precisely, using a party of Japanese tourists as cover, two Chinese artists bounded half-naked on to Tracey Emin's My Bed at the Tate Gallery, had a slightly half-hearted pillow fight and then shouted something unfathomable in Mandarin.

To muted applause from bemused gallery-goers, unsure whether they were witnessing a protest against the visit of President Jiang Zemin or some bizarre comment on Emin's Turner Prize exhibit, the men then tried to take a swig from one of Emin's empty vodka bottles. With security guards closing in, the pantomime came to a swift and sweaty end despite the artists' attempt to fend them off with their best Bruce Lee karate moves.

The Battle of the Bed may have been all over in a few minutes but it will go down in art history as the defining moment of the new and previously unheard of Anti-Stuckist Movement.

That much can be discerned from the slogans scrawled on JJ Xi and Yuan Chai's bodies. Most, however, were unhelpfully in Chinese. (The Stuckists are a group led by Emin's ex-boyfriend Wild Billy Childish.)

Unfortunately Xi and Chai were unable to perform the "critical sex" they had hinted at. Earlier both men had said they felt "a sexual act was necessary to fully respond to Tracey's piece".

My Bed, the most talked about Turner Prize exhibit in years, is the divan in which Emin "almost went out of her mind in for four days" this summer, complete with skid-marked sheets, used condoms, soiled knickers and all the detritus of a "lost" weekend.

The Turner Prize exhibition was closed to the public after the incident. Last night as Tate curators started the long and arduous task of putting Emin's bed back into its original dishevelled state, Xi, 37, and Chai, 43, were in the cells of Belgravia police station explaining their "intervention" to police. "We usually get a different type of artist down here," said one officer.

Both men were later released without charge. A Scotland Yard spokeswoman said neither the "gallery nor the artist had any desire to bring the matter further".

Xi and Chai have a reputation for satirical "interventions". Xi scattered a room with £1,200 at Goldsmith college, south London, and let the audience scramble for the cash to highlight the greed of the art market, and both men used mock street signs to confuse the movers and shakers attending the Venice Biennale two years ago.

They insist their performance was not an attack on Emin. "We are simply trying to react to the work and the self-promotion implicit in it. I hope the security guards see it in that spirit."

They didn't, although some who witnessed their intervention drew that distinction and booed the police and security guards as they led the men from the gallery.

Tanith Freeborn, from Bristol, who witnessed the bed-hopping, said it had made her weekend. "I get a bit worried about people messing with works of art but this seemed to be in the right spirit.

"I was watching Emin"s film about her abortion next door when I heard this strange shouting. I went into the other room and these two Chinese guys were jumping about on the bed naked from the waist up. The guards looked stunned.

"After a few minutes of hopping about and shouting I think they ran out of things to do. If they had tried to wreck it, or stolen the vodka or her knickers, I might have felt differently. It made my weekend."

A spokeswoman for the Tate said: "The work has now been restored and the exhibition will open to the public as usual at 10am." She refused to discuss what had been done to "restore" it.

Film-makers Steve McQueen and the Wilson Twins, and the photographer Steve Pippin, are the other artists nominated for the Turner Prize. The winner will be announced on November 30.